China's Tianwen-1 Mars mission is arriving at the red planet: What you need to know

On July 22 2020, the Chinese space agency sent a trio of spacecraft on a daring mission to land on Mars. Known as Tianwen-1 (loosely translated to "questions to Heaven"), the craft contains a Mars orbiter, lander and a rover that is expected to reach the surface sometime in May. Leading up to launch last year, the hype was high -- but it was almost impossible to find a livestream. 

"In the months running up to a major mission, there's close to radio silence, which is frustrating," says Andrew Jones, a journalist who reports on China's space program for SpaceNews.com. "We didn't get anything for Chang'e-4 until landing success was confirmed." 

But dozens of private broadcasts ensured avid rocket fans could see the Long March 5 carrying Tianwen-1 leave the Earth.   

The Chang'e-4 mission to the moon is one of the crowning achievements of the Chinese space exploration program. In January 2019, China was able to deliver a rover to the lunar far side -- the first time a nation had achieved such a feat. Unlike the recent NASA and SpaceX mission to the International Space Station, the launch of Chang'e-4 was not broadcast across the globe in real-time. There was no livestream for launch and no shots of Chinese mission control celebrating when the scientists and engineers learnt of their success.

On Chinese social media network Weibo, it was a different story. Quanzhi Ye, an astronomer at the University of Maryland, says the Tianwen-1 hasthag on Weibo generated 29,000 tweets and 150 million reads in the week prior to launch.  

Ye notes it's not unusual for China to be quiet before the mission, but also says he has observed an improvement in the communication over the last decade, noting "nowadays you can see scientists discussing mission concepts on media outlets and lots of discussion on the Chinese space program happening on Weibo."

Even with a lack of information from CNSA, Tianwen-1 is a big deal for space exploration globally. When it arrives at Mars on Feb. 10, it will spend time orbiting the planet, before dropping its lander and rover down to the surface later in the year. If successful, China will become just the third nation to achieve a landing on Mars. 

The Tianwen-1 mission

Landing on the moon is difficult -- and landing on its far side even more so -- but Mars is a whole different kettle of cosmic fish. The red planet was at its closest point to Earth in late July 2020, at around 36 million miles (58 million kilometers), but Tianwen-1 will still have to navigate a much greater distance to land on Mars' surface sometime in May 2021. That requires a good deal of navigational accuracy and a terrifying descent to the surface. As the US and Russia are well aware, Mars is notoriously good at killing off robotic explorers. Over 50% of the missions sent to the red planet fail.

The Chinese mission will kick the difficulty up a few more notches. Tianwen-1 is a triple threat: It contains an orbiting spacecraft, a lander and a rover. 

"Tianwen-1 is going to orbit, land and release a rover all on the very first try, and coordinate observations with an orbiter," the mission's chief scientist wrote in a short article for the journal Nature Astronomy on July 13. "No planetary missions have ever been implemented in this way."

Scientific objectives of Tianwen-1

With three spacecraft headed to Mars, China hopes to provide a "global and extensive survey of the entire planet" while using the rover to examine locations on the surface with high scientific interest. 

As detailed by the article in Nature, there are five core science objectives first laid out in 2018:

• Create a geological map of Mars
• Explore the characteristics of the Martian soil and potentially locate water-ice deposits
  
• Analyze the surface material composition
  
• Investigate the Martian atmosphere and climate at the surface
  
• Understand the electromagnetic and gravitational fields of the planet

The orbiter is equipped with seven instruments. It contains two cameras, a subsurface penetrating radar, a spectrometer to reveal the mineral composition of the surface and instruments to analyze charged particles in the Martian atmosphere. 

The rover, which is about twice the mass of China's lunar Yutu-2 rover at around 240 kilograms (530 pounds), contains six instruments and also includes two cameras, as well as radar and three detectors which can be used to understand the soil composition and magnetic fields of Mars.

The landing site for the rover has been the subject of speculation, but the Nature article confirms it will be somewhere in Utopia Planitia, a vast plain in Mars' northern latitudes and the same place NASA's Viking 2 mission landed in the 1970s. The expected touchdown date is approximately two to three months after Tianwen-1 arrives in Mars orbit so, if all goes to plan, we can expect it sometime in April or May 2021.  

Mars is the place

July 2020 was an impressively busy time for Mars and Martian explorers, but February is set to be even busier.

Not only will China's Tianwen-1 insert itself into orbit, but the United Arab Emirates have sent their own Martian explorer to the red planet: an orbiter named Hope. The orbiter will examine and analyze the thin atmosphere on Mars to try and assess why it's so unusual.

NASA, too, is getting in on the Earth exodus. The space agency launched its Perseverance rover on July 30 last year. The next-gen rover is carrying a helicopter known as Ingenuity, a tech demonstration that aims to become the first vehicle to fly across the surface of another planet. 

All three missions have been travelling through space for seven months. They're now entering the final phase of their cruise. By the end of February, Mars will have a host of new robot companions in orbit and on its surface -- should all go well.

Editor's note: This article has been updated since publication in July 2020, in anticipation for Tianwen-1's arrival at Mars.